[backend] crop effective confidence level in [0-100]

[labo-flg]

Closes #5759

Proposed changes

• user_effective_level is cropped between [0-100] on computation, that's all
• no cropping when adding/editing the confidence values of users and groups. Thus we cannot trust them for now (this might be addressed in Enforce input validation against schema for patching object attributes #5696 as part of a new validation against schema, including such numerical constraints)
• adding confidence information to the internal user in context ; for use internnaly
• built-in users have a confidence level now (all to 100 so they can do their job correctly).
• updated test base to improve coverage

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

This PR replaces #5768

[labo-flg]

I moved this function as an utility and added unit tests

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (0c34913) 64.81% compared to head (e335973) 65.57%.
Report is 8 commits behind head on master.

Files	Patch %	Lines
...encti-platform/opencti-graphql/src/types/user.d.ts	0.00%	3 Missing ⚠️
...ncti-platform/opencti-graphql/src/types/group.d.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5787      +/-   ##
==========================================
+ Coverage   64.81%   65.57%   +0.75%     
==========================================
  Files         521      523       +2     
  Lines       61347    61438      +91     
  Branches     4899     5568     +669     
==========================================
+ Hits        39762    40285     +523     
+ Misses      21585    21153     -432     

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[SarahBocognano]

Tested ✅ Works fine !